1. Field of the Invention
The invention relates in general to beam-activated objectformation systems and relates in particular to novel methods and apparatus by means of which such systems may be employed for the construction of objects having complex geometrical form.
It is to be noted, however, that while the invention will be described with reference to particularized methods, embodiments and end uses, the invention is not limited to such particularizations. Those having ordinary skill in the art and access to the teachings of this specification will recognize additional implementations and utilization within the invention's scope.
2. Background Art
The composition and structure of underground geologic formations can be of enormous significance for disciplines such as natural-resource prospecting and earthquake prediction. Considerable effort is accordingly expended on the process of first obtaining and then analyzing data concerning such formations.
It is in the analysis phase of this process, however, that the format in which obtained data is presented to a human interpreter often significantly impacts the extent to which intra-data patterns can be perceived and their associated geophysical significance fully ascertained. This format dependence can be seen in the case of the three-dimensional reflective seismic survey, which is currently the principal technique for collecting data regarding the subject formations. Because the typical first-stage output of such a survey is a voluminous matrix of numerical values which in themselves are of limited comprehensibility, an attempt is usually made to convert the output into a more user-compatible form. The industry thus makes extensive use of expedients such as two-dimensional visual graphics of either hard-copy or computer-display variety. Furthermore, output visual effects of a pseudo three-dimensional nature are also currently achievable through an augmentation of the two-dimensional media by means of such additional graphical techniques as isometric contouring employing either color coding or perspective views.
Although these full two-dimensional and pseudo three-dimensional approaches are often very useful for a broad range of interpretive purposes, it has now been perceived that there are numerous instances where the availability of a true three-dimensional physical model of the subject formations would be decidedly advantageous. However, the typically-complex nature of these formations, in conjunction with the necessity for representational accuracy, renders conventional model-building techniques, which are usually manually-implemented, either physically inadequate or economically prohibitive.
An alternative technology which initially presents itself as a candidate for desired model-construction tasks is the ensemble of beam-activated object-formation techniques whose fundamental concepts are set forth in patents issued to W. K. Swainson. (See, for example, U.S. Pat. Nos. 4,041,476 and 4,238,840, as well as related U.S. Pats. Nos. 4,078,229; 4,288,861 and 4,333,165). Basically, the U.S. Pat Nos. 4,041,476 and 4,238,840 and references disclose apparatus for producing a three-dimensional model which includes a volume of liquid medium characterized by its solidification where impinged upon by intersecting energy beams of uniquely different properties.
While U.S. Pat. No. 4,041,476 (col. 12, line 10-12) and U.S. Pat. No. 4,238,840 (col. 10, line 64-66) suggest that underground geologic formations are a class of objects which can be effectively reproduced in three dimensions through the use of the disclosed system, neither reference teaches anything which, as a practical matter, would enable one to do so.
The U.S. Pat. Nos. 4,041,476 and 4,238,840 references disclosed a pattern-dependent, pattern-sequenced approach in which a reproduced surface is constructed by directly tracking the loci of points on the surface to be copied. The practical obstacles encountered in the use of such surface tracking are a consequence of the approach's failure to address three concurrent constructional requirements; namely, first, viewability of presently-constructed volume elements; second, non-blockage of subsequently-constructed volume elements; and third, element supportability.
The "viewability" requirement can best be illustrated by reference to the U.S. Pat. No. 4,041,476 reference's method, wherein an object is formed by means of constructional "writing" at a beam-illuminated intersection point located within an object-formation medium. It is apparent that a given point must be viewably accessible by the beams in order for them to intersect and the writing to be consequently effectuated.
The difficulty is in attempting to assure such viewability at all regions of a given complex surface, which can include multiple peaks and valleys, overhangs and other complex formations.
The "non-blockage" requirement, referred to earlier, is related to the "viewability" requirement in that a written point in the object-formation medium should not block the writing of a subsequent point. As it is not difficult to conceive of written blockages which no possible repositioning of write beams could circumvent, the rotating surface-tracking approach disclosed in the two references does not solve this second of the complex-modeling requirements.
The third requirement of surface-element supportability concerns the practical necessity for assuring that a given written element be provided with some form of structural support. While the sequential element-to-element progression which characterizes the aforemetioned references' surface-tracking technique tends to assure that each written point of a simple surface will be supported by virtue of being contiguously disposed to the most-recent previously-written element, such is not the case with the modeling of complex surface formations wherein, for example, the tip of an overhang might be encountered prior to its supporting portion. Further, the unresolved problems of viewability-obstruction and subsequent-element blockage can prevent significant portions of the desired model from being sequentially constructed.
It thus becomes apparent that although the references' general suggestions envisions complex surface modeling, they contain nothing which points the way toward the construction of complex objects such as true three-dimensional representations of underground geologic formations.